1. Field of the Invention
The present invention relates to the artificial logs used in a gas fireplace, and in particular to improved aesthetics, heat generation and combustion emissions.
2. Related Information
Gas log sets are made of ceramic or concrete logs and a burner assembly fueled by natural gas, propane and in some cases butane. These gaseous fuels typically burn with a blue flame. In order to market these log sets the manufacturers have attempted to make the logs look real and have tweaked the burner to produce a dancing and flickering flame with yellow tips.
The gas log sets are typically set up with a burner assembly buried in a media such as sand, vermiculite, glass shards or cinders. The premixed gas and air are percolated up through the media where it is ignited to produce flames which flicker about the ceramic logs which are formed and colored to resemble wooden logs. xe2x80x9cRock Woolxe2x80x9d chunks are placed on the top of the media to simulate wood embers. The flames heat the edges of the xe2x80x9cRock Woolxe2x80x9d making them red hot and glowing. These embers somewhat simulate wool embers but they can contribute to the formation of soot, especially if burning propane or butane, by providing a surface where the hydrocarbons can pyrolize. xe2x80x9cRock woolxe2x80x9d (also called mineral wool, mineral cotton, silicate cotton, and slag wool) is known in the art as a substance outwardly resembling wood, having a mass of interlaced filaments, made by subjecting furnace slag and some minerals with a strong blast while molten.
The United States Occupation Safety and Health Administration recognizes three general groups of Synthetic Mineral Fibers. They are fiber glass (glasswool and glass filament), mineral wool (rockwool and slagwool) and refractory ceramic fibers (RCF). Fiber glass and mineral wool are generally made by blowing or drawing fibers from a molten mass. Refractory ceramic fibers are generally made by chemical reactions, precipitation or vapor phase deposition. Refractory ceramic fibers (RCF) can have a higher porosity and surface roughness than the other groups of fibers and can also have higher chemical purity. All these differences are beneficial for applying and presenting catalysts. Refractory ceramic wool is produced by making a low density pad or mat of randomly oriented ceramic fibers of relatively short length. The resultant mat resembles wool pieces. Of special importance is the fiber diameter. Fibers smaller than 3 microns are considered to be respirable and damaging to lungs. Refractory ceramic fibers can be produced larger than 3 microns.
It is an advantage of the present invention that the amount of radiant energy from a fireplace is increased. A further advantage is that the emissions of hydrocarbons, nitrogen oxides and carbon monoxide are reduced. It is an additional feature that the present invention improves the aesthetics of a gas flame.
Briefly, the present invention is a synthetic ember comprising refractory ceramic wool pieces coated with an oxidation catalyst for use as embers in a gas-fired log set or fireplace. The oxidation catalyst may be selected from the group consisting of Pt, Pd, Rh, Co, Mn and mixtures thereof, preferably in the amount about 0.10 wt. % to about 5.0 wt. %. More preferably the oxidation catalyst comprises Pt. Preferably the refractory ceramic wool is comprised of filaments and has a surface area of from 20 to 200 square meters per gram and a density of 0.01 to 0.05 grams per cubic centimeter. Preferably the catalytic embers are less than one inch square and preferably less than one-half square inches each. Preferably the refractory ceramic fibers have diameters 3 microns and larger.